Means for connecting coaxial line with slow wave circuit

ABSTRACT

Means for electrically connecting a coaxial line with a slow wave circuit in a satisfactory manner, that is, in such a manner as to avoid reflection at the portion of connection and to produce a mechanically strong connection.

United States Patent Inventor Appl. No

Filed Patented Assignee Priority Shigetsugu Watanabe Kawasaki-shi, Japan June 27, 1968 Apr. 6, 1971 Matsushita Electric Industrial Co., Ltd. Osaka, Japan July 11, 1967, July 12, 1967 Japan 42/45174 and 42/45408 MEANS FOR CONNECTING COAXIAL LINE WITH SLOW WAVE CIRCUIT 2 Claims, 5 Drawing Figs.

[51] Int. Cl ..H01r17/04, HOlp 3/08 [50] Field ofSearch 339/177, 178,179, 212; 333/31 (Main), 6, 84 (M), 96, 97

,[56] References Cited UNITED STATES PATENTS 2,035,545 3/1936 Green 333/96X 2,805,399 9/1957 Leeper 339/177X(E) Primary Examiner- Ernest R. Purser Assistant Examiner-Lawrence J. Staab Attorney-Stevens, Davis, Miller & Mosher ABSTRACT: Means for electrically connecting a coaxial line with a slow wave circuit in a satisfactory manner, that is, in such a manner as to avoid reflection at the portion of connection and to produce a mechanically strong connection.

Paten td 'April6, 1971 3,573,687-

; 2 Shasta-Sheet 1 INVENTOR AT'I'OR NliY- MEANS FOR CONNECTENG COAXIAL LINE WITH SLOW WAVE CIRCUIT The present invention relates to connecting means adapted to provide satisfactory matched connection between a coaxial line and a shielded slow wave circuit, e.g. of a structure such as a travelling wave deflecting line for ultrabroadband cathode ray tubes.

In connecting individual ultrahigh frequency signal transmission systems with each other, reflection has frequently occurred at the connecting portion due to unsatisfactory registration, even when the substantial characteristic impedances of said respective transmission systems were the same. Matching at the connection portion has been particularly difficult when lines of different structure, such as a coaxial line and a slow wave circuit, were connected with each other.

It is the object of the present invention to provide connecting means by which a coaxial line and a shielded slow wave circuit are connected with each other with satisfactory matching therebetween.

ln order that the present invention may be fully understood, reference will be made to the accompanying drawings, which illustrate the invention by way of example as applied to the connection between the input-output terminal of a travelling wave deflecting line for a ultrabroadband cathode ray tube using a flat strip helix, and a coaxial connector, and in which:

FIG. 1 is a vertical cross-sectional view of the connecting means according to the present invention as used for connection between the coaxial line and the slow wave circuit;

PK]. 2 is a transverse cross-sectional view taken along the line ll-ll ofFlG. 1;

FIG. 3 is a vertical cross-sectional view showing, in an enlarged scale, the connecting end portion of the inner conductor of the coaxial line; and

H08. 4a and 4b are a top plan view and a side view respectively of the connecting terminal end of the strip conductor of the slow wave circuit.

Referring to the drawings, reference numeral 1 represents the inner conductor of a signal transmitting coaxial line and 2 represents the outer shielding conductor which is provided with an external thread 3 at one end thereof. A collar 4 adapted to engage said threaded end 3 of the outer shielding conductor is securely fixed on the outer conductor 5 of a slow wave circuit. lnterior of the outer conductor 5 is disposed a flat strip helix which is composed of a dielectric 8 having a strip conductor 7 helically wound therearound, and which is secured to the inner wall of said outer conductor through the intermediary of a dielectric 9. The terminal 71 of the strip conductor 7 extends into through holes 12 and 11 formed in the dielectric 9 and the outer conductor 5 respectively, with its end extremity bent into an inverted L-shape. The bent end portion of the terminal 71 is formed with an internally threaded hole 72 for engagement with a tapered external thread 6 provided at the connecting end of the inner conductor l of the coaxial line. Incidentally, the top surface of the bent end portion of the terminal 71 of the strip conductor 7 is flush with the contacting surfaces of the outer conductor 5 and bearing 4.

Reference numeral 10 represents a dielectric supporting the inner conductor 1, which dielectric may be made from glass or ceramic so that it may simultaneously serve as an airtight connecting terminal of the coaxial line. In connecting the slow wave circuit and the coaxial line of the structures described above, the outer conductor 2 is screw threaded into the bearing 4 at the externally threaded end 3, while simultaneously screwing the external thread 6 into the internally threaded hole 72 in the bent end portion of the inverted L-shaped terminal 71 of the strip conductor 7, whereby electrical and mechanical connections between the outer conductors 2 and 5 and between the inner conductor 1 and the strip conductor 7, can be achieved simultaneously.

ln this case, since the external thread 6 at the end extremity of the inner conductor 1 of the coaxial line is tapered toward its end, a tight engagement is produced between the larger diameter root portion of the external thread 6 and the internal thread of the hole 72 in the bent end portion of the terminal 71 of strip conductor 7, and thus the rigid connection between said inner conductor 1 and said strip conductor 7 is enhanced.

lt is also to be noted that by differentiating the pitches of the external threads 3 and 6, it is possible to urge the terminal of the strip conductor 7 toward or away from the coaxial cable, thereby improving the contact between the inner conductor 1 and the strip conductor 7. The connecting means of the present invention is so designed that the inverted L-shaped terminal 71 of the strip conductor is brought into contact with the dielectric 10 when the external thread 3 on the outer conductor 2 has been fully screw threaded into the bearing 4.

A substantial adjustment of impedance at the connecting portion can be attained by varying the diameters of the through hole 12 in the dielectric 9 and through hole 11 in the outer shielding conductor 5, and by varying the dimensions of the flat strip helix. The impedance may also be adjusted by varying the length of the externally threaded portion 6 at the end extremity of the inner conductor 1.

As will be understood from the foregoing, it is possible, according to the embodiment of the invention illustrated herein, to connect the coaxial line with the flat strip helix at right angles thereto, while maintaining satisfactory matching therebetween. The present invention is particularly adapted for use with a slow wave circuit which is sealed in a cathode ray tube, because by employing the present connecting means it is possible to feed a signal directly to the deflecting line from a coaxial line in a transverse direction, i.e. in a perpendicular direction, to the tube. The connecting means of the invention as described above can be applied, not only to the deflecting line for a travelling wave-type cathode ray tube wherein use is made only of a flat strip helix, but also to delay circuits of other structures.

As described hereinabove, by employing the present inven tion a signal transmitting coaxial cable and a slow wave circuit can be connected with each other with satisfactory matching therebetween, and the impedance at the connecting point can be easily adjusted by properly selecting the sizes of the holes in the shielding conductor and dielectric of said slow wave circuit. Further, according to the invention, since the core wire of the coaxial line is screw threaded into the terminal of the slow wave circuit, simultaneously as the outer conductor of said coaxial line is screw threaded into a portion of the wall of the outer shielding conductor of said slow wave circuit, there can be produced a highly rigid electrical and mechanical connection between said coaxial line and said slow wave circuit, which may further be enhanced by differentiating the pitches of the respective threads.

lclaim:

1. Means for connecting a coaxial line with a slow wave cir cuit, characterized by an external thread provided on the outer conductor of the signal transmitting coaxial cable of said coaxial line and screw threaded into a portion of the wall of the outer shielding conductor of said slow wave circuit, and an external thread of different pitch provided at an end of the inner conductor of said coaxial line and screw threaded into the terminal of said slow wave circuit through holes bored in said outer shielding conductor and a dielectric supporting the inner conductor of the slow wave circuit to be secured thereby.

2. Means for connecting a coaxial line with a slow wave circuit according to claim 1, wherein the terminal of a strip conductor composing the slow wave circuit is flexed in an inverted L-shape and threadably engaging the end of the inner conductor of the coaxial cable at its flexed end portion. 

1. Means for connecting a coaxial line with a slow wave circuit, characterized by an external thread provided on the outer conductor of the signal transmitting coaxial cable of said coaxial line and screw threaded into a portion of the wall of the outer shielding conductor of said slow wave circuit, and an external thread of different pitch provided at an end of the inner conductor of said coaxial line and screw threaded into the terminal of said slow wave circuit through holes bored in said outer shielding conductor and a dielectric supporting the inner conductor of the slow wave circuit to be secured thereby.
 2. Means for connecting a coaxial line with a slow wave circuit according to claim 1, wherein the terminal of a strip conductor composing the slow wave circuit is flexed in an inverted L-shape and threadably engaging the end of the inner conductor of the coaxial cable at its flexed end portion. 